1. Technical Field
This invention is generally related to the field of peptide probes, to the field of peptide probes for the detection of amyloid aggregation, and to the field of peptide probes for the rapid and specific detection of amyloid aggregation.
2. Prior Art
Aggregation of a 39-43 amino acid peptide, beta amyloid (Aβ) (Kang, J., et al., The precursor of Alzheimer's disease amyloid A4 protein resembles a cell-surface receptor, Nature 325, 733-736, 1987; Roher, A. E., et al., beta-Amyloid-(1-42) is a major component of cerebrovascular amyloid deposits: implications for the pathology of Alzheimer disease, Proc Natl Acad Sci USA 90, 10836-10840, 1993), into a fibril via formation of nuclei (Kusumoto, Y., et al., Temperature dependence of amyloid beta-protein fibrillization, Proc Natl Acad Sci USA 95, 12277-12282, 1998; Teplow, D. B., et al., Elucidating amyloid beta-protein folding and assembly: A multidisciplinary approach, Acc Chem Res 39, 635-645, 2006; Fernandez-Busquets, X., et al., Recent structural and computational insights into conformational diseases, Curr Med Chem 15, 1336-1349, 2008; Lazo, N. D., et al., On the nucleation of amyloid beta-protein monomer folding, Protein Sci 14, 1581-1596, 2005; Wetzel, R., et al., Plasticity of amyloid fibrils. Biochemistry 46, 1-10, 2007) is believed to be implicated in the pathology of Alzheimer's disease (AD), which is a neurodegenerative disorder characterized by a progressive loss of cognitive functions and by neuropathological features comprising amyloid deposits and neuronal losses in the brain (Hardy, J., et al., The amyloid hypothesis of Alzheimer's disease: progress and problems on the road to therapeutics, Science 297, 353-356, 2002; Mattson, M. P., Pathways towards and away from Alzheimer's disease, Nature 430, 631-639, 2004; Haass, C., et al., Soluble protein oligomers in neurodegeneration: lessons from the Alzheimer's amyloid beta-peptide, Nat Rev Mol Cell Biol 8, 101-112, 2007).
Low molecular weight Aβ species, such as monomers and dimmers, are not toxic (Haass, C., et al., (2007) Soluble protein oligomers in neurodegeneration: lessons from the Alzheimer's amyloid beta-peptide, Nat Rev Mol Cell Biol 8, 101-112, 2007; Kayed, R., et al., Common structure of soluble amyloid oligomers implies common mechanism of pathogenesis, Science 300, 486-489, 2003; Kayed, R., et al., Permeabilization of lipid bilayers is a common conformation-dependent activity of soluble amyloid oligomers in protein misfolding diseases, J Biol Chem 279, 46363-46366, 2004; Klyubin, I., et al., Amyloid beta protein immunotherapy neutralizes Abeta oligomers that disrupt synaptic plasticity in vivo, Nat Med 11, 556-561, 2005). A considerable amount of data has identified the soluble Aβ oligomers as potentially significant toxic agents (Haass, C., et al., Soluble protein oligomers in neurodegeneration: lessons from the Alzheimer's amyloid beta-peptide, Nat Rev Mol Cell Biol 8, 101-112, 2007; Glabe, C. G., Common mechanisms of amyloid oligomer pathogenesis in degenerative disease, Neurobiol Aging 27, 570-575, 2006). However, the possibility that the AR fibrils may be associated with neurotoxicity cannot be ruled out, since fibrillar aggregates can serve as a pool of soluble intermediate species through a dynamic exchange with monomers or oligomers (Id.; O'Nuallain, B., et al., Thermodynamics of A beta(1-40) amyloid fibril elongation, Biochemistry 44, 12709-12718, 2005; Martins, I. C., et al., Lipids revert inert Abeta amyloid fibrils to neurotoxic protofibrils that affect learning in mice, EMBO J 27, 224-233, 2008). Toxic oligomers are kinetic intermediates, and can display changes in conformation and toxic effects by subtle environmental changes (Teplow, D. B., et al., Elucidating amyloid beta-protein folding and assembly: A multidisciplinary approach, Acc Chem Res 39, 635-645, 2006; Wetzel, R., et al., Plasticity of amyloid fibrils, Biochemistry 46, 1-10, 2007; Haass, C., et al., Soluble protein oligomers in neurodegeneration: lessons from the Alzheimer's amyloid beta-peptide, Nat Rev Mol Cell Biol 8, 101-112, 2007; Klyubin, I., et al., Amyloid beta protein immunotherapy neutralizes Abeta oligomers that disrupt synaptic plasticity in vivo, Nat Med 11, 556-561, 2005).
Determination of population profiles of different aggregate species is strongly required to understand the molecular causes of Aβ aggregation as well as toxic processes in AD. However, the complex nature of Aβ aggregation, including the generation of transient aggregate intermediates, impedes the establishment of a functional correlation between AR aggregation characteristics and their cellular/clinical manifestations. A quantitative measurement of aggregate species must be done rapidly without significant perturbation of samples for high level accuracy, as aggregates including toxic soluble oligomers are likely to undergo further structural changes during the additional sample preparation and incubation steps (Haass, C., et al., Soluble protein oligomers in neurodegeneration: lessons from the Alzheimer's amyloid beta-peptide, Nat Rev Mol Cell Biol 8, 101-112, 2007; Chromy, B. A., et al., Self-assembly of Abeta(1-42) into globular neurotoxins. Biochemistry 42, 12749-12760, 2003; Hoyer, W., et al., Dependence of alpha-synuclein aggregate morphology on solution conditions, J Mol Biol 322, 383-393, 2002). Rapid and specific detection of distinct amyloidogenic species is therefore quintessential for the establishment of a reliable correlation between aggregation profiles and their cellular/clinical manifestations as well as achieving better understanding of the determinants of aggregation.
Inaccurate quantification of various aggregate species would result in the gap seen between basic scientific discovery and cellular/clinical manifestations, and the discrepancy among observations from animal model studies. The currently available compounds or methods, however, either do not distinguish different aggregate species or are inappropriate for rapid, non-perturbative detection due to the requirement of additional sample preparation and incubation steps (Kayed, R., et al., Common structure of soluble amyloid oligomers implies common mechanism of pathogenesis, Science 300, 486-489, 2003; Williams, A. D., et al., Structural properties of Abeta protofibrils stabilized by a small molecule, Proc Natl Acad Sci USA 102, 7115-7120, 2005; Kayed, R., et al., Conformation-dependent anti-amyloid oligomer antibodies, Methods Enzymol 413, 326-344, 2006; Kayed, R., et al., Fibril specific, conformation dependent antibodies recognize a generic epitope common to amyloid fibrils and fibrillar oligomers that is absent in prefibrillar oligomers, Mol Neurodegener 2, 18, 2007; Linke, R. P., et al., High-sensitivity diagnosis of AA amyloidosis using Congo red and immunohistochemistry detects missed amyloid deposits, J Histochem Cytochem 43, 863-869, 1995; LeVine, H., 3rd, Quantification of beta-sheet amyloid fibril structures with thioflavin T, Methods Enzymol 309, 274-284, 1999).
Accordingly, there is always a need for improved probes for the detection of amyloid aggregation. There also always is a need for improved peptide probes for the rapid and specific detection of amyloid aggregation. It is to these needs, among others, that this invention is directed.